Sigma 18-50 f/2.8

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petemc

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Does anyone have any samples of this lens at 18mm f/2.8? I've seen some shots that show its super sharp at 50mm at like f/2.8 but thats pointless for me as I have the Canon 50mm f/1.8. I'd be buying it to have the f/2.8 constant aperture through out the 18-50mm range. The samples I've seen online kinda make me wonder. I haven't actually seen a sharp shot at 18mm. I've seen some stunningly sharp shots from the 24-70 so I'm more tempted by that lens but I would prefer the range of the 18-50.
 
Yeah I spent hours on there. Nothing. Maybe it just isn't sharp at 18mm f/2.8. I'm after a semi-wide angle lens to do portraits but I want a nice depth of field and sharp people. This is why I'm tempted by the 24-70. But his pics never seem wide enough.
 
Thanks but thats at f/4 not f/2.8. I'm after portrait shots at f/2.8 with it. Like in the link I put above.
 
i have some but they are editted low light pictures taken at iso1600 so are about as much use as a chocolate teapot in the sharpness stakes


ill try to take something tomorrow for you if i get the chance
 
Fair enough. Well I've trawled through a lot of lens reviews over the last year or so and the general theme seems to be that zooms in the 24-70 range are sharper than zooms in the 18-50 range, at least across the frame. There are several 18-50 type zooms that have impressive centre resolution, even at f/2.8, but they fail at the borders. The 24-70s don't seem to be as bad.

But if you really want to do low light stuff, get a fast prime. The 50mm f/1.4 is great and reasonably cheap if you can live with the focal length. I couldn't (found it far too close for general purpose stuff) so I went for the 35L which is dear but it seems to be the only sub-50mm L-series prime which is sharp across the frame. Most of the others suffer from the same centre/corner imbalance as the 18-50s. Even the 24L.

Of course this is a very broad overview and it's based on my impressions from trawling www.photozone.de, www.fredmiranda.com and www.photo.net.
 
Sorry, I already said in my opening post I have the Canon 50mm f/1.8. Thats why I'm looking for pictures taken at 18mm f/2.8. The Tamron 18-35 is sharp at f/2.8 but at 35mm its f/4. So thats pretty useless. It looks like the Sigma 24-70 is my best bet for a cheap sharp lens.

I'm off to Toronto in just over a week you see. I have the Sigma 10-20 for city and landscapes. I'm not taking my Canon 100-400 as its an extra weight I don't need. I can just take my old Canon 80-200. I have the Canon 50mm f/1.8 for low light stuff. I also have a Canon 28-105mm f/3.5 - something. But I want wider lens for low light stuff and for one for doing street photography with a nice depth of field. The Sigma 24-70 lens seems like the best thing to buy. But I was hoping to see if the 18-50 was better for getting a better depth of field on a wider angle.
 
Well at 18mm f/2.8 the Sigma is plenty sharp in the centre, ok at the borders and pretty poor at the extreme borders. See here for review (skip to the MTF resolution figures at the bottom - I regard anything over 1700 as decent and anything over 2000 as brilliant):
http://www.photozone.de/8Reviews/lenses/sigma_1850_28/index.htm

If you can live with the poor extreme borders and the fact that it's not as good at 50mm as 18mm then you should buy it.

If you can't live with that, may I suggest this for street work:
http://www.photozone.de/8Reviews/lenses/canon_24_28/index.htm

Warehouse Express have it for £309 and the resolution figures look decent.
 
I'd prefer to see real world examples :) Stats don't sell things to me, this sells. Thats why I'm very tempted by the 24-70. Looks excellent. If I could only see some images from the 18-50 like that then I would buy it as I've seen if for £250.
 
You do realise that it's impossible to tell how sharp a lens is from a websize picture, right?

At those dimensions, I could take a picture on the kit lens and make it look every bit as bright and sharp at that photo. It's only at 100% you notice where the money's going.
 
Ok put it this way. I've seen far sharper shots from the 24-70 at f/2.8 than I have of the 18-50 at f/2.8.

Those shots are great. The last one is very sharp and almost what I'm after. I guess I'm just have to go find this lens and try it out.
 
Have you compared examples from the same photographer? Or has it been different users for each lens, in the examples you've seen? I'd be absolutely astounded if you could tell the difference on 640 x 400ish shots, especially after sharpening in PS.
 
But have you seen shots from the same people taken on the 18-50? I ask because processing plays such a massive part in it, as I'm sure you know. The HDR stuff you did looks great but it didn't look like that straight out the camera. So if I was trying to see whether I should buy a Sigma 12-24 (or whatever the range is) those shots would be little use.

Even photos that look natural will have had processing. Take this for example. It's got 15 layers in Photoshop. There's no way you could tell whether any of that was down to the lens.
 
I get all that. But there is a certain level of sharpness that is hard to fake. If sharpness was simply a matter of processing then why even bother buying expensive glass? This is getting silly. I haven't seen any examples of the types of photography I want to do with the 18-50. I'll see if I can find one locally to test. If it does the job then I'll buy it. If not I'll try the 24-70. I was hoping someone had the examples I was after, clearly not.
 
Yes, you can't fake sharpness. But when you're looking at a 640 x 4XX images, the 8 MP original can be fairly soft and still look good shrunk down.

All you really need for websize images to look super-sharp is zero motion blur and proper focus. If you've got those two things, you can make an impressive on-screen 'print'.

Anyway, no. You want examples of it at f/2.8, 18mm and I steer clear of that wherever possible so I don't have what you're after. Using any lens at maximum aperture isn't ideal. I bought some f/1.4 glass so that it would look decent at f/2.8. I very rarely use it at f/1.4.
 
hi pete, i never got round to it this evening but ill try to take some test shots


is sharpness across the entire frame at f2.8 really important though? surely if your using it at such a wide aperture your going to be wanting to blur the background anyway, and very rarely would the drop off in sharpness be noticed at the edge of the frame anyway unless you purposefully put your focal object right on the edge of the frame, just my random thoughts
 
I used the 18-55 Nikkor for a couple of months earlier this year and was very impressed by it at all apertures and focal lengths.
That doesn't help you obviously, but I found that you never get stellar performance from Sigmas compared to Marque lenses. If you can find the cash go for a Canon or Nikkor (depending on which you use, natch) - it'll always be better.
 
Yeah I know that Canon would be sharper but it would also be 2x as heavy and 2x as pricey and I'm spending 3 weeks in Toronto so I don't quite fancy blowing loads of cash on a lens.
 
I think your going to have to try and find a Jessops or Jacobs, or other shop that has one in and take a close look yourself, tight timing, but its the only way to be sure and get a copy thats good.
 
I appreciate that, but there's a reason it's twice as heavy and twice the price - the quality is better.

If you want the Sigma then there are compromises in design and manufacture you have to accept - you pays yer money and takes yer chances.
 
Ummmm, save some cash and buy one there?
 
To be fair to pete, the Sigma 18-50mm f/2.8 is about £250, whereas the only Canon that competes is the brand new 17-55mm f/2.8 (the rest aren't constant wide aperture) and that's about £900, so the price difference for a bit of extra edge sharpness (lab tests show centre performance is similar, especially at 18mm) and slightly less CAs is pretty hefty.

In general, a bit of extra quality costs a lot of extra money so I can see why he's keen to keep it cheap.

Pete, I know you love your ultra-wide shots and it seems to me like you have your heart set on being able to work at 18mm with a wide aperture. The 24-70s might be sharper but if it's the 18mm length you want (and if I'm any judge of character, it seems like you do) then go for that. Focal length is one of the few things you can't change in photoshop.
 
Oh, what about the Sigma 17-70mm f/2.8-4.5? I know it's not constant f/2.8 but (a) it's still f/2.8 at the wide end, which is what you seem to want most and (b) it's meant to be good value for money.

Edit: Just checked the resolution figures and it does seem to be worse at the wide end than the 18-50mm. Particularly the extreme borders which are ****-poor, if the numbers are anything to go by.
 
Arkady said:
I appreciate that, but there's a reason it's twice as heavy and twice the price - the quality is better.

If you want the Sigma then there are compromises in design and manufacture you have to accept - you pays yer money and takes yer chances.
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Yeah I fully appreciate that too :) Just that I've seen sharp results from a few people and thats what I want too :) I'd love to buy the Canon but I can't afford to. Even if I did knowing that its just as heavy as the 100-400 makes me doubt it as a "walk around lens" :)

dod said:
Ummmm, save some cash and buy one there?
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One store is selling it for £290. A saving of £9 :D Silly Canadian money doesn't appear to save me anything.

fingerz said:
To be fair to pete, the Sigma 18-50mm f/2.8 is about £250, whereas the only Canon that competes is the brand new 17-55mm f/2.8 (the rest aren't constant wide aperture) and that's about £900, so the price difference for a bit of extra edge sharpness (lab tests show centre performance is similar, especially at 18mm) and slightly less CAs is pretty hefty.

In general, a bit of extra quality costs a lot of extra money so I can see why he's keen to keep it cheap.

Pete, I know you love your ultra-wide shots and it seems to me like you have your heart set on being able to work at 18mm with a wide aperture. The 24-70s might be sharper but if it's the 18mm length you want (and if I'm any judge of character, it seems like you do) then go for that. Focal length is one of the few things you can't change in photoshop.
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Yeah. I love the freedom my 10-20 gives me and its a bit hard giving that up now :) Non of the Liverpool stores had the 18-50 in so I bought a 24-70 to roadtest. Initial impressions are that it seems faster than when I tested one before Xmas. Oh I wanted constant f/2.8 for gig work too :)
 
petemc said:
Initial impressions are that it seems faster than when I tested one before Xmas.
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Dunno about the weather where you are but it's a lovely day down here, which is nice but not ideal for testing fast lenses. When you get a really overcast day, that's when you get to see if it's got the speed you need. I speak from months of experience wandering around Shepherds Bush on lunch breaks, getting blurry shots because the weather doesn't suit my determination to stay in ISO 100.
 
Thanks :) I'm meeting up with Dave who already knew about this. We'll be popping around those places on the Sunday. The Saturday is AnimeNorth \o/ :D
 
petemc said:
Thanks :) I'm meeting up with Dave who already knew about this. We'll be popping around those places on the Sunday. The Saturday is AnimeNorth \o/ :D
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Very good then, have fun! I'll be there on Saturday. Should be lots to see, I wanna see some pics then eh!! :D

Cheers,

Jewel
 
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